A curved mirror adjustment device including a curved mirror and a mirror holding member configured to hold the curved mirror has been known (see, for example, Patent Literature 1). The curved mirror adjustment device described in Patent Literature 1 includes: a first angle adjustment mechanism configured to adjust the angle of the curved mirror by rotating the curved mirror about a first axis, which is orthogonal to an optical axis, as a rotation axis; a second angle adjustment mechanism configured to adjust the angle of the curved mirror by rotating the curved mirror about a second axis, which is orthogonal to the optical axis and the first axis, as a rotation axis; a first position adjustment mechanism configured to adjust the position of the curved mirror by translating the curved mirror in a direction parallel to the first axis; and a second position adjustment mechanism configured to adjust the position of the curved mirror by translating the curved mirror in a direction parallel to the second axis. The curved mirror adjustment device further includes a fixation member to which the mirror holding member is fixed.
In the curved mirror adjustment device described in Patent Literature 1, the mirror holding member includes a first holding member and a second holding member. The second position adjustment mechanism is a washer disposed between the first holding member and the second holding member and/or a washer disposed between the second holding member and the fixation member. In the adjustment device, the washers are disposed between the first holding member and the second holding member and the washers are disposed between the second holding member and the fixation member on both sides in the first axial direction. Thus, by changing the thickness or number of the washers disposed on one side in the first axial direction and the thickness or number of the washers disposed on the other side in the first axial direction, the curved mirror can be rotated about the optical axis as a rotation axis to adjust the angle of the curved mirror.